Fluid dispensing in a range of picoliters (pL) to microliters (μL) is often used in biological and pharmaceutical research and development, medical diagnosis and examination, or agricultural testing. For example, in studying a dose-response effect of chemotherapy, fluid dispensing with a low volume is an important task for determining the concentration of a candidate compound required to effectively attack cancer cells.
In such dose-response experiments, candidate compounds are prepared at many different concentrations in wells of a multiwell plate to determine an effective concentration. An existing on-demand type of droplet ejecting apparatus is used for the above application. For example, the droplet ejecting apparatus includes a storage container that holds a solution, a nozzle that ejects the solution supplied from the container, a pressure chamber between the container and the nozzle, and an actuator that controls pressure inside the pressure chamber to eject the solution from the nozzle.
In the droplet ejecting apparatus, the volume of one droplet ejected from an individual nozzle is on the order of a picoliter (pL). By controlling the total number of droplets ejected into each well, the droplet ejecting apparatus supplies an amount of fluid in a range of picoliters to microliters into each well. Therefore, the droplet ejecting apparatus is generally suitable for dose-response experiments when dispensing the candidate compounds at various concentrations or when dispensing in very small amounts.
A multiwell plate (also referred to as a microplate) normally used in this context has 1,536 wells (hereinafter, this multiwell plate may be referred to as a 1,536 well plate). Efforts have also been made to use a microplate having 3,456 wells (hereafter, referred to as a 3,456 well plate) and a microplate having 6,144 wells (hereinafter, referred to as a 6,144 well plate). However, in microplates having more than 1,536 wells, the wells must typically be very densely arranged. Though, it is possible to improve experimental evaluation efficiency by increasing the number of samples and to improve reagent utilization efficiency since the volume of the wells is usually smaller.